Disclosed embodiments relate to drive and dosing devices for an injection device having a mechanism for preventing the setting of a dose which exceeds the amount of product present in a cartridge. The drive and dosing device serves the purpose of dispensing a fluid product, particularly a medicament.
The term “medicament” includes any flowable medical formulation suitable for controlled administration though, for example, a cannula or a hollow needle and comprises a liquid, a solution, a gel or a fine suspension containing one or more medical active ingredients. A medicament can be a composition comprising a single active ingredient or a pre-mixed or co-formulated composition with more than one active ingredient present in a single container. Medication includes drugs such as peptides (e.g., insulin, insulin-containing drugs, GLP-1 containing drugs or derived or analogous preparations), proteins and hormones, active ingredients derived from—or harvested by—biological sources, active ingredients based on hormones or genes, nutritional formulations, enzymes and other substances in both solid (suspended) or liquid form but also polysaccharides, vaccines, DNA, RNA, oligonucleotides, antibodies or parts of antibodies but also appropriate basic, auxiliary and carrier substances.
Injection devices such as injection pens are known from the state of the art. Individual doses of a product can be set and subsequently dispensed with such injection devices. This procedure can be repeated several times. Because the amount of medicament present in the cartridge is limited, namely often 300 International Units (IU), a dose may be set above the amount that can be dispensed from the cartridge, particularly the nominal volume, which is also called the in the cartridge contained volume. This could result in, for example, 35 IU being set while only 20 IU can be dispensed with a subsequent injection. The difference of 15 IU is missing in the medication. A user of the device might not notice this which can lead to hazardous adverse dosing.
From the state of the art other dosing devices are proposed which prevent setting a dose which exceeds the amount of product present in the cartridge. For example, in FIG. 3 of WO 2001/019434, a device is proposed having a drive sleeve surrounding a piston rod having at its outer surface a thread engaging an inner thread of a stop nut. The stop nut has a recess and a sleeve surrounding the stop nut such that the stop nut is in a rotational secure and axially slidable engagement with the sleeve. If the outer sleeve is rotated relative to the drive sleeve, which happens during dose setting, then the stop nut co-rotates and screws itself along the thread of the drive sleeve towards a stop position. During dose delivery, the stop nut stands still with respect to the drive sleeve and the outer sleeve thus building a counting mechanism counting the set and dispensed doses. At the attempt of setting a dose which exceeds the amount of product present in the cartridge, the stop nut abuts a catch on the drive sleeve and blocks a further increase of dose setting such that the setting of a dose exceeding the amount present in the cartridge is prevented.
An alternative example device with an identical effect is shown in WO 2007/017052. Amongst other features, a stop nut is described that is in a threaded engagement with an outer thread present at a piston rod. The piston rod is rotatable with respect to the housing for dispensing a set dose and is also in a threaded engagement with the housing such that a rotation of the piston rod causes the piston rod to move in the dispensing direction. During setting of a dose which would exceed the amount of product present in the cartridge, the stop nut hits a mechanical stop present at the proximal end of the piston rod whereby the mechanism is blocked, and the setting of a dose exceeding the amount present in the cartridge is prevented.
In WO 2005/018721, an injection device is described having a dose knob that can be rotated relative to a housing for setting a dose and that rotation is transmitted to a dose setting member or scale drum. During dispensing, the dose knob is rotationally decoupled from the scale drum. Thus, during dose delivery the knob is pressed with the thumb and this knob does not rotate relative to the housing versus the scale drum that rotates back into the device.
In WO 2004/020027 an injection device is described having a dose knob for setting a dose and an overload protection for the dose setting mechanics. For example, if a user wants to over-torque the dose knob when the rotation is in principle blocked by the dose setting mechanics, thus preventing damage to the mechanical components of the system.